Nationals backbencher Ken O'Dowd has said he wanted the issue resolved as soon as possible.

"I hope this doesn't go on too much longer," he told reporters in Canberra this morning. "I'd hope to have it resolved today or tomorrow."

Mr O'Dowd said he did not think any of his colleagues will move against Mr Joyce, preferring instead to have "a talk" to him about his future. "Someone needs to tell him where the party stands at this stage."

This photo, published by the Daily Telegraph, shows Mr Joyce sneaking a peek at then-media adviser Vikki Campion at a farm summit in Sydney in November 2016.

Nationals MP George Christensen criticised MPs pushing for a change in leadership, telling The Australianthey did not have the numbers to call for a spill or move a motion of no confidence.

He confirmed that "individual" MPs had raised concerns with Mr Joyce about his future.

Senior Liberal and Finance Minister Mathias Cormann insisted the Liberal and National parties remained in a "strong, united coalition".

"The leadership of the National Party is very much a matter for the National Party," he told ABC News Breakfast.

Asked whether he was prepared to take on the role of Acting Prime Minister - which would be the case if Mr Joyce resigned from his position - Mr Cormann said: "I think you're getting way ahead of yourself. The acting Prime Minister (is) usually and always, unless he is away, Deputy Prime Minister, and I would expect that to be the case next week."

Cabinet minister and Queensland MP David Littleproud told ABC Radio that Mr Joyce had the support of most Nationals MPs.

Queenslander Michelle Landry likewise confirmed her support for the Deputy leader: "Barnaby will remain our leader. He has done a lot for us, particularly in regional Australia and I think we should give him a fair go with it."

Labor MP Stephen Jones called for Mr Joyce to step down, telling reporters in Canberra that Malcolm Turnbull should step in if they can't come to a resolution.

"It's time for Barnaby Joyce to do the right thing by the country, by his party and step down. And, if he is not going to do that, if the National Party can't sort out their own issues, then the Prime Minister has to act."

Reports Nationals have already begun discussions with Mr Joyce follow suggestions his senior colleagues were planning to "formally tap" the leader on the shoulder, according to ABC reports.

The increasing speculation comes amid fears Mr Joyce was losing his support base in Queensland over the scandal.

Former Nationals leader Warren Truss said on Tuesday night Mr Joyce continuing as leader of the Nationals was "a matter for his parliamentary colleagues".

While Mr Truss believes Mr Joyce had "enormous capabilities", he said the situation needed to be resolved "constructively and quickly so that the business of government can proceed".

Barnaby Joyce said former staffer Vikki Campion was ‘without a shadow of a doubt’ his partner.

Earlier Tuesday, reports revealed Mr Joyce spent 50 nights in Canberra on the taxpayers' purse when Parliament wasn't sitting - more nights than any other Turnbull government minister.

Fairfax Media reported official expense records show the embattled politician claimed $16,690 in travel allowance for out-of-session nights in the first nine months of 2017.

The amount exceeded that of any other top government official, including Treasurer Scott Morrison, Finance Minister Mathias Cormann and Foreign Minister Julie Bishop.

Mr Joyce was acting Prime Minister for 10 of the 50 nights. He was entitled to claim $276 per night for official business as Deputy Prime Minister and $565 per night as acting Prime Minister.

He also claimed for 62 sitting nights, spending a total of 112 days in Canberra out of 272 days.

Vikki Campion’s former fiancee John Bergin as he appears in his Twitter profile Twitter profile at https://twitter.com/theburgerman

Mr Joyce's office said his stays in Canberra were a result of his electorate not having permanent commonwealth offices like capital cities.

"It should be expected that the Deputy Prime Minister would use the Canberra Office more frequently than those Ministers who have capital city bases," a spokesperson told Fairfax.

Malcolm Turnbull was on drawn into the saga again Tuesday when asked by the Parliament this question: when does a lover become a partner?

The matter is critical because if the Deputy Prime Minister's new partner, pregnant former staffer Vikki Campion, was his de facto, her movement among offices would have breached ministerial guidelines barring jobs for relatives.

But if she had the status of friend or lover, the moves were acceptable.

Questions have been raised around Ms Campion's move from Mr Joyce's office to the office of Resources Minister Matt Canavan, back to Mr Joyce's office, and then to the office of the National Party Whip Damian Drum.

A spokesman for the PM had told AAP Mr Joyce had not breached ministerial standards in regard to the employment of family and partners because Ms Campion was not his "partner" at the time of her appointments.

"Those statements … followed a background discussion and were not authorised by me," Mr Turnbull said.

"As the Deputy PM confirmed in his statement of Saturday, February 10, and again in his statement this morning, the Nationals are responsible for decisions relating to staffing in the office of Nationals' members," he told Parliament.

Mr Joyce yesterday confirmed Ms Campion was now officially his partner, and detailed how their relationship developed after she began working in his office.

He said Ms Campion joined his staff for the July, 2016 election in New England. In August she joined his ministerial staff.

"A friendship subsequently developed and that became, over time, more," he added.

Ms Campion was due to marry her then partner John Bergin that November, but called off the engagement three months before the date.

She is now pregnant and due to give birth in April.

The affair and pregnancy also led to the end of Mr Joyce and wife Natalie's 24-year marriage. In a statement delivered outside Parliament on Tuesday, the Nationals leader accepted responsibility for the breakdown marriage breakdown, and apologised to the women it had affected.

Barnaby Joyce and his wife Natalie have split after 24 years. Picture: Ray Strange

"I would like to say to Natalie how deeply sorry I am for all the hurt this has caused. To my girls, how deeply sorry I am for all the hurt it has caused them," he told reporters outside federal parliament on Tuesday.

"To Vikki Campion, how deeply sorry I am that she has been dragged into this. Later in a written statement, Mr Joyce said his marriage was under pressure for some time.

"Natalie and I tried to make it work again in April last year but it subsequently came to an end," he said.

"This has been a searing personal experience for Natalie, our daughters and for Vikki - criticise me if you wish but please have some regard for them." He also apologised to voters in his New England electorate for "this personal issue" going public.